Control of the filling level of silver reservoirs in the textile industry

ABSTRACT

A method and apparatus for standardizing the cross section or weight per unit length of a sliver produced by a textile machine which supplies material to a sliver reservoir includes the correcting of long-term fluctuations in the material at the outlet of the machine by controlling the supply of material at the inlet of the machine and the correcting of short-term fluctuations in the material at the outlet of the machine by variably drafting the material at the outlet of the machine. A minimum filling level and a lower than minimum filling level of the sliver reservoir is monitored so that the short-term fluctuations may be controlled in response to the minimum filling level and the long-term fluctuations may be controlled in response to the lower than minimum filling level of the sliver reservoir. Thus, the average filling level of the reservoir is controlled on the basis of the size of the fluctuations in this filling level.

United States Patent Felix et al.

[ Jan. 28, 1975 I CONTROL OF THE FILLING LEVEL OF SLIVER RESERVOIRS IN THE TEXTILE INDUSTRY [75] Inventors: Ernst Felix; Peter Feller, both of Uster, Switzerland [73] Assignee: Zellweger, Ltd., Uster. Switzerland [22] Filed: Dec. 22, 1972 [21] Appl. No.: 317,771

Primary Examiner-Dorsey Newton Attorney, Agent, or Firm-Craig & Antonelli [57 ABSTRACT A method and apparatus for standardizing the cross section or weight per unit length of a sliver produced by a textile machine which supplies material to a sliver reservoir includes the correcting of long-term fluctuations in the material at the outlet of the machine by controlling the supply of material at the inlet of the machine and the correcting of short-term fluctuations in the material at the outlet of the machine by variably drafting the material at the outlet of the machine. A minimum filling level and a lower than minimum filling level of the sliver reservoir is monitored so that the short-term fluctuations may be controlled in response to the minimum filling level and the long-term fluctuations may be controlled in response to the lower than minimum filling level of the sliver reservoir. Thus, the average filling level of the reservoir is controlled on the basis of the size of the fluctuations in this filling level.

5 Claims, 8 Drawing Figures [52] US. Cl. 19/240 [51] Int. Cl D0lh 5/32 [58] Field of Search 19/239, 240, 241; 226/42, 226/44 [56] References Cited UNITED STATES PATENTS 2,147.421 2/1939 Bendz 226/42 2,147,467 2/1939 Stephenson... 226/42 3.184.798 5/1965 Burnet et a1. 19/240 X 3,403,426 10/1968 Stiepel et al..,... 19/240 3,703,023 11/1972 Krauss et al. 19/240 DRIVE CONTROL i UNIT CONTROL PATE .JAN28I975 I NTED SHEEN, aesama PATENIEDJAN28I975 3,862,473

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CONTROL OF THE FILLING LEVEL OF SLIVER RESERVOIRS IN THE TEXTILE INDUSTRY This invention relates to the control of the filling level of sliver reservoirs in the textile industry.

Sliver reservoirs are commonly used for equalisation between the delivery of an intermediate product from one production machine and the pickup of this intermediate product by the following machine. When both machines are adjusted to the same output, the sliver reservoirs need only contain a relatively small sliver reserve, whereas in the case of production lines with highly fluctuating production, these sliver reservoirs have to be kept suitably filled.

However, it is not only between different production stages that the interposition of sliver reservoirs is called for, as there are also types of machine in which internal production and consumption have to be equalised at one or more places to guarantee uninterrupted production. One example of a machine of this kind is an adjustable card which incorporates two types of regulating system,'namely a first for eliminating prolonged or long term fluctuations in the form of a controlled variable rotational speed of the feed roller, and a second for standardising short-term fluctuations which acts on the card sliver in the form of a draft means. For example, a sliver reservoir is required between a front roller of the draft means with variable speed for regulating purposes and the feed means delivering the sliver to the sliver coiler which is driven at a constant speed, to equalise the fluctuations in production of the card sliver due to the regulation. To this end, the sliver reservoir requires a monitoring means which prevents excessive fillings or excessive removal of sliver. Since the effect of the sliver reservoir is intended to be satisfactory under all the working conditions occurring, the average filling level has to be so high that, in even the most unfavourable case, complete emptying never occurs. However, a sliver reservoir is attended by the serious disadvantage that if the sliver reservoir is overfull the sliver to be removed from the reservoir has to be withdrawn with a relatively thick layer of sliver piled on top so that due to its loose cohesion it is readily damaged or torn.

An object of the present invention is to obviate these disadvantages. The invention accordingly provides a method of controlling the filling level of a sliver reservoir in the textile industry, especially in spinning, in which the average filling level of the sliver reservoir is controlled on the basis of the size of the fluctuations in this filling level.

The invention also provides an apparatus for carrying out this method, comprising at least one sensor for detecting a minimum quantity of sliver in the reservoir and means for controlling the quantity of sliver delivered to and/or removed from the sliver reservoir on the basis of the signal released by the sensor.

In the. accompanying drawings:

FIG. 1 is a graph of a number of statistical distributions,

FIG. 2 is another graph of statistical distributions in another arrangement,

FIG. 3 diagrammatically illustrates the principle of a sliver reservoir with a sensor for the filling level,

FIG. 4 is a graph illustrating a controlled filling level,

FIG. 5 is a block diagram illustrating the connection of the sensor to the regulating mechanism,

FIG. 6 is an enlarged detail from a graph illustrating a statistical distribution,

FIG. 7 diagrammatically illustrates the principle of a sliver reservoir with a sensor for the filling level and a safety device, and

FIG. 8 is a block diagram illustrating the connection of another sensor to the regulating mechanism.

FIG. I is a frequency diagram illustrating the distribution of the filling of a sliver reservoir in a regulated textile machine, for example a card. In the event of regulation, this frequency follows very closely a normal distribution so that the laws of statistics applying to the normal distribution can be applied at least approximately to this frequency. The references 1, 2 and 3 denote different degrees of the coefficients of variation of the filling, curve 1 embodying a large coefficient of variation, curve 2 an average coefficient and curve 3 a very small coefficient of variation. All three degrees can occur in one and the same machine. In the absence of an arrangement according to the invention, the average filling of the sliver reservoir would have to be fixed at such a value that, in the case of highly irregular material (curve 1), the state of complete emptying occurs so rarely that it can still be borne in practice. In the case of curve 1, this would be the value M. In the processing of a material with relatively small fluctuations in filling, for example according to curve 2 or even curve 3, complete emptying of the sliver reservoir would never occur in practice and the sliver would always have to be removed under an unnecessarily large quantity of sliver.

However, the average length of sliver present in the sliver reservoir could be selected smaller, the better the uniformity of the filling or its variation coefficient. Accordingly, it would always be possible to work with a minimum permissible filling if the variation coefficient of the filling were known, diminishing the problem of withdrawing the further-transported sliver under one or more layers of stored sliver.

This is also shown in the graph according to FIG. 2, in which the middle lines M of the distribution curve 1, 2, 3 are displaced along the abscissa. The displacements have taken place to such an extent that the ordinate axis x is situated at a tolerable frequency value 1 l, for example one percent of the total frequency. This produces the frequency curve 1 with its central axis M1 for a large variation coefficient, the frequency curve 2' with its central axis M2 for an average variation coefficient and the frequency curve 3' with its central axis M3 for a small variation coefficient of the filling level of the sliver reservoir.

The fluctuations in the filling level under consideration are a function of time. Accordingly, it is also permissible to express the remaining frequencies 11 as a time fraction of a predetermined, sufficiently large representative time interval.

FIG. 3 shows a first embodiment of the invention for controlling the filling level of a sliver reservoir. The references l4, l5 and l6, l7 denote paired rollers of a drafting arrangement for a card sliver 10 whose draft is controlled, such as disclosed in copending application Ser. No. 286,865, filed Sept. 7, 1972, for example, on the basis of a measuring signal formed from the cross-section of the card sliver in a measuring unit 18. The card sliver 10 is deposited in the actual sliver reservoir, the container 20, by a pair 19 of transporting rollers. A second pair 21 of transporting rollers removes the card sliver 10 from the container 20 and delivers it, for example to a so-called can stock or sliver coiler, by way of a pair of rollers 22, filling the card sliver into spinning cans. The location of the sliver reservoir is not of crucial significance to the control of the filling level of the sliver reservoir.

Inside the sliver reservoir 20 there is a first sensor 23 which always releases a certain electrical signal when, after leaving the pair of transporting rollers, the card sliver 10 falls downwards under its own weight. This function can be performed for example by a photocell arrangement known per se. If then the filling of the sliver reservoir 20 decreases (for a reason to be explained further on) to such an extent that the card sliver 10 no longer covers the bottom of the container 20, but passes with a free sag 10 from the pair of rollers 19 to the pair of rollers 21, the sensor 23 will respond. In this case, increased follow-up of the card sliver is necessary and can be achieved by increasing the delivery of material at the input end of the card through the control system so that the follow-up of the card sliver is also increased by the then necessary higher draft in the drafting arrangement 14-17. After a while therefore the sag 10" will become greater and the card sliver 10' will begin to be re-deposited on the bottom of the container 20 so that the sensor 23 will no longer respond, stopping the increased delivery of material. After a certain time, therefore, a condition will prevail in which the sagging sliver 10" will cover the sensor 23 for a certain time interval and expose it for another, on average, longer, time interval.

In this connection, it'is desirable that the sliver reservoir should on the average be emptied to a very slight extent, i.e., that the quantity of sliver removed should be somewhat greater than the quantity of sliver introduced on the average. Accordingly, after a certain period of time, the sliver reservoir will of necessity be increasingly emptied, giving rise to the increased followup in accordance with the cycle described earlier on. FIG. 4 shows the path followed by the average filling level as a function of time. At the time t t t the sliver reservoir is empty to such an extent that the sensor 23 releases a signal. This in turn releases the increased follow-up until the flow of material returns to normal through disappearance of the signal. When the gradual emptying which begins again leads to release of the signal, the cycle is repeated in the manner described.

If the card sliver shows pronounced irregularities, the filling in the sliver reservoir will also be subjected to considerable fluctuations. The frequency of certain fillings will substantially follow the curve 1 in FIG. 1.

In the event of minor fluctuations in the cross-section of the card sliver 20, the supply of material controlled by the periodic response of the sensor 23 will also deposit a certain supply of sliver in the reservoir and use it up again at shorter time intervals. Accordingly, the average filling level remains low.

FIG. 5 is a diagrammatic plan view of a card with a feed roller 31 and the controlled drive 32 for the main cylinder, feed roller and doffer, the pairs 14-17 of drafting rollers with a rotational speed control 33, and a control unit 34 which converts the signals of the sensor 23 and of the measuring unit 18 into control commands for the controllable drives 32 and 33, respectively.

Since the filling level of the sliver reservoir 20, is, as already mentioned, largely subject to the laws of normal distribution and since as required a small fraction of the fillings of the sliver reservoir or an inadequate follow-up occurs during a fraction of a sufficiently long time interval, it can happen as a so-called rear occurrence that the supply of card sliver in the sliver reservoir 20 is completely used up and the sag also below the permitted limit. FIG. 6 shows the beginning of the branch of a normal distribution curve, that part of the filling which occurs in less than 1 percent of the random tests according to the filling level (or in less than 1 percent of a certain sufficiently long time interval) being limited to the abscissa 0.

If a condition such as this (filling level dropping below a permitted minimum) occurs, the card sliver will tear in the absence of special measures because the offtake over the pair of rollers 21 is greater than the follow-up supplied by the pair of rollers 19.

Initially, however, the sag in the card sliver 10 (FIG. 3) will be further reduced where permitted by the cohesive force of the fibre material.

Accordingly, the limit 0 is not identical with the limit at which the sliver would tear, instead it is even further to the left. At the same time, the probability value also falls appreciably, for example from I percent to 0.! percent. 1

If this condition of a minimum permitted sag is detected by another source 24 (FIG. 7) and on the basis of this detection acts on those parts of the machine responsible for follow-up of the sliver in the sense that more sliver is supplied, for example by interrupting or limiting regulation of the rotational speeds of the rollers, the danger of the card sliver tearing through inadequate capacity of the sliver reservoir is eliminated. The objection that some of the card sliver is processed with unregulated draft in this way, can be overcome on the grounds that this condition occurs on average for only 0.1 percent of the working time and the disadvantage of a sliver regulated to a limited extent in regard to its cross-section over a limited length is less serious than tearing of the sliver in the sliver reservoir.

Accordingly, the arrangement according to the invention functions in a balanced condition in such a way that the card sliver 10 issuing from the pair of rollers 19 passes between at least one sensor 23 and/or 24 and is run off by the pair of rollers 21.

These sensors are arranged in such a way that the first sensor 23 is influenced in the event of excessive sag of the card sliver 10 while the second, 24, is influenced in the event of excessive tension in the card sliver and releases a signal. The signal released by the first sensor 23 regulates the delivery of fibrous material at the input 31 and hence a maximum filling level of the sliver reservoir 20 through the cross-sectional measurement of the card sliver 10 produced and the control of draft derived therefrom in the drafting arrangement 14-17. The second sensor 24 acts as a limiting or safety means in those cases where the filling level would theoretically exceed a permitted minimum in order to avoid any interruption in the flow of material.

FIG. 8 is a diagrammatic plan view of a card followed by a regulated drafting arrangement, a sliver reservoir and a sliver coiler. The second sensor 24 acts on the controllable drive 33 through the control unit 35. This influence on draft regulation in the case of response of the second sensor 24 has to take place without any delay because the sensor only comes into operation after the last sliver reserve has been used up and no more material is available for equalisation.

Any type of sensor can be used for the sensors 23 and 24, for example mechanical sensors which are deflected by the card sliver, or photocells which have the advantage of being able to function as sensors in the absence of any contact. Capacitive sensors can also be used.

What we claim is:

1. In a method for standardizing the cross section or weight per unit length of a sliver produced by a textile machine including the steps of measuring the supply of material at the outlet of the machine, drafting the material at the outlet of the machine, correcting long-term fluctuations in the material at the outlet of the machine by controlling the supply of material at the inlet of the machine in response to the measured supply of material, correcting short-term fluctuations in the material at the outlet of the machine in response to the measured supply of material by altering the draft thereof, and adjusting the difference between the variable rate of the short-term correction operation and the rate of travel of the sliver by supplying said sliver to a sliver reservoir, the improvement comprising the steps of monitoring a minimum filling level and a lower than minimum filling level of the sliver reservoir and, as a result of such monitoring, controlling the long-term fluctuations in response to the lower than minimum filling level and controlling said correction of short-term fluctuations in response to the minimum filling level in such a way that the average filling level of the sliver reservoir is controlled on the basis of the size of said fluctuations in this filling level.

2. A method as defined in claim 1 wherein said step of correcting short-term fluctuations is temporarily inhibited upon detection of said less than minimum filling level in the sliver reservoir.

3. In an apparatus for standardizing the cross section or weight per unit length of the sliver produced by a textile machine having a feed roller at the inlet thereof, comprising measuring means for measuring the cross section of the sliver at the output of said textile machine, first regulating means responsive to said measuring means for controlling the speed of the feed roller of said textile machine to control the supply of material received at the inlet end of the textile machine and second regulating means in the form of a drawing arrangement including a rear pair of cylinders connected to said textile machine to be driven therewith, a front pair of cylinders, and drive means responsive to said measuring means for driving said front pair of cylinders at a variable rate to correct short-term fluctuations in the material received at the outlet of said textile machine, a sliver reservoir receiving the sliver obtained from said second regulating means, the improvement comprising first and second detection means for generating respective signals representative of the minimum filling level and a less than minimum filling level of said sliver reservoir, respectively, first control means responsive to said second detection means for influencing said first regulating means to increase the supply of material to the inlet of the machine, and second control means responsive to a signal from said first detection means for influencing said second regulating means in such a way that the filling level of the reservoir is controlled on the basis of the size of the fluctuations of this filling level.

4. Apparatus as defined in claim 3 wherein-said second detection means includes a first sensor for detecting said less than minimum level in said sliver reservoir and for providing a signal in response thereto, said first control means being responsive to the signal from said first sensor for controlling said first regulating means to increase the quantity of sliver supplied to said sliver reservoir.

5. Apparatus as defined in claim 4 wherein said first detection means includes a second sensor for detecting said minimum quantity of sliver in said sliver reservoir and for providing a signal in response thereto, said second control means being responsive to the signal from said second sensor for inhibiting said second regulating means to increase the supply of sliver to said sliver reservoir. 

1. In a method for standardizing the cross section or weight per unit length of a sliver produced by a textile machine including the steps of measuring the supply of material at the outlet of the machine, drafting the material at the outlet of the machine, correcting long-term fluctuations in the material at the outlet of the machine by controlling the supply of material at the inlet of the machine in response to the measured supply of material, correcting short-term fluctuations in the material at the outlet of the machine in response to the measured supply of material by altering the draft thereof, and adjusting the difference between the variable rate of the short-term correction operation and the rate of travel of the sliver by supplying said sliver to a sliver reservoir, the improvement comprising the steps of monitoring a minimum filling level and a lower than minimum filling level of the sliver reservoir and, as a result of such monitoring, controlling the long-term fluctuations in response to the lower than minimum filling level and controlling said correction of short-term fluctuations in response to the minimum filling level in such a way that the average filling level of the sliver reservoir is controlled on the basis of the size of said fluctuations in this filling level.
 2. A method as defined in claim 1 wherein said step of correcting short-term fluctuations is temporarily inhibited upon detection of said less than minimum filling level in the sliver reservoir.
 3. In an apparatus for standardizing the cross section or weight per unit length of the sliver produced by a textile machine having a feed roller at the inlet thereof, comprising measuring means for measuring the cross section of the sliver at the output of said textile machine, first regulating means responsive to said measuring means for controlling the speed of the feed roller of said textile machine to control the supply of material received at the inlet end of the textile machine and second regulating means in the form of a drawing arrangement including a rear pair of cylinders connected to said textile machine to be driven therewith, a front pair of cylinders, and drive means responsive to said measuring means for driving said front pair of cylinders at a variable rate to correct short-term fluctuations in the material received at the outlet of said textile machine, a sliver reservoir receiving the sliver obtained from said second regulating means, the improvement comprising first and second detection means for generating respective signals representative of the minimum filling level and a less than minimum filling level of said sliver reservoir, respectively, first control means responsive to said second detection means for influencing said first regulating means to increase the supply of material to the inlet of the machine, and second control means responsive to a signal from said first detection means for influencing said second regulating means in such a way that the filling level of the reservoir is controlled on the basis of the size of the fluctuations of this filling level.
 4. Apparatus as defined in claim 3 wherein said second detection means includes a first sensor for detecting said less than minimum level in said sliver reservoir and for providing a signal in response thereto, said first control means being responsive to the signal from said first sensor for controlling said first regulating means to increase the quantity of sliver supplied to said sliver reservoir.
 5. Apparatus as defined in claim 4 wherein said first detection means includes a second sensor for detecting said minimum quantity of sliver in said sliver reservoir and for providing a signal in response thereto, said second control means being responsive to the signal from said second sensor for inhibiting said second regulating means to increase the supply of sliver to said sliver reservoir. 